1. Field of the Invention
The invention relates to a key signal-generating device for a keyboard, and more particularly, to a key signal-generating device with a trench to release air.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram of a prior art key signal-generating device 10. FIG. 2 is a section view along line 2xe2x80x942 of the prior art key signal-generating device 10 of FIG. 1. The key signal-generating device 10 generates key signals in a keyboard. The key signal-generating device 10 has a thin film circuit board 18 to generate key signals, and a plurality of rubber domes 20 on a top surface 22 of the thin film circuit board 18 to support a key 16. The rubber dome 20 is fixed by a glue layer 30 to the top surface 22 of the thin film circuit board 18.
As shown in FIG. 2, the thin film circuit board 18 has a plurality of pressure sensors 32 that correspond to the rubber domes 20. Each rubber dome 20 has a base 24, a predetermined space 26 filled with air within the rubber dome 20, and an orifice 28 in the base 24 to communicate the pressure in the predetermined space 26 with the atmosphere. When a user presses the key 16, the rubber dome 20 is squeezed by the key 16 to activate the pressure sensor 32, and a signal is generated correspondingly. The air in the predetermined space 26 is released to the outside atmosphere through the orifice 28, as shown by arrow 34.
But the prior art key signal-generating device 10 has some defects. First, the orifice 28 is formed in the base 24, so the thickness of the base cannot be reduced. Second, while the rubber dome 20 is being fixed onto the thin film circuit board 18, the orifice 28 must be carefully aligned with an indenture 31 in the glue layer 30 shown in the FIG. 1, or the orifice 28 will be blocked by the glue of the glue layer 30 and the key signal-generating device 10 will malfunction.
It is therefore a primary objective of the present invention to provide a key signal-generating device with a trench to release air from the hollow rubber dome to solve the above-mentioned problem.
According to the claimed invention, the key signal-generating device has a trench to release air. The device includes a thin film circuit board set on a base to generate key signals. The thin film circuit board has a top side and at least one trench on the top side. The device also includes at least one hollow rubber dome set on the thin film circuit board that extends out from the top side of the thin film circuit board to provide elastic support for a key structure. The rubber dome has a predetermined space that is filled with air. One end of the trench extends into the predetermined space so that the predetermined space is in communication with the atmosphere. When the key structure is pressed, the rubber dome is squeezed down by the key structure, causing air in the predetermined space to be released to the atmosphere through the trench.
It is an advantage according to the present invention that the key signal-generating device with a trench to release air has a thinner base and is easier to assemble.
These and other objects and the advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.